1. Field of the Invention
The invention relates to a height control valve for a vehicle air suspension, and, more particularly, to a height control valve with dual ride height positions.
2. Description of Related Art
Trailing arm suspensions are well known and are commonly used in heavy-duty vehicles, such as semi-tractors, trailers, buses, and recreational vehicles. A trailing arm suspension typically includes opposing trailing arm assemblies mounted to frame rails on opposite sides of the vehicle. Each of the trailing arm assemblies includes a trailing arm having one end pivotally connected to a hanger bracket suspended from the frame rail. The other end of the trailing arm mounts to an air spring, which is also mounted to the frame rail. The air spring dampens the pivotal rotation of the trailing arm about the hanger bracket relative to the frame rail.
An axle assembly typically spans and mounts to, or is carried by, the trailing arms. The axle assembly rotatably mounts ground-engaging wheels. Any movement of the wheels in response to their contact with the ground will result in a rotation of the trailing arms, which is dampened by the air springs.
The air springs typically include an air bag from which pressurized fluid can be introduced or exhausted to adjust the dampening performance of the air spring. Additionally, the volume of air in the air spring can be adjusted to alter the height of the frame rails relative to the trailing arms. Often, there is a preferred ride height for the vehicle and, depending on the load carried by the vehicle, the ride height can vary. Pressurized air is introduced to or exhausted from the air bags to adjust the relative height of the trailer frame rail with respect to the trailing arms for a particular load.
The adjustment of the ride height is traditionally accomplished by a height control valve having an inlet port, an air spring port, and an exhaust port. The inlet port is in fluid communication with the pressurized air system of the vehicle, the air spring port is in fluid communication with the air bags of the air springs, and the exhaust port is in fluid communication with the atmosphere. The height control valve is moveable between a neutral position, in which the air spring port is blocked, and fill and exhaust positions. In the fill position, the air spring port is placed in fluid communication with the inlet port to introduce pressurized air to the air springs, and in the exhaust position, the air spring port is placed in fluid communication with the exhaust port to exhaust air from the air springs. The valve typically has a housing that is mounted to the vehicle frame, and a lever arm mounted to the trailing arm or axle. Movement of the lever relative to the valve housing is indicative of the relative change in position between the trailing arm and the vehicle, and moves the valve between its neutral, fill, and exhaust positions.
One type of height control valve includes a disc that rotates with respect to a housing between the neutral, fill, and exhaust positions (see, e.g., U.S. Pat. No. 7,028,996). Air pressure within a chamber of the housing forces a portion of the disc into sealing engagement with the housing. The disc covers an air spring port in the housing when in the neutral position. As the disc rotates to the fill and exhaust positions, the air spring port is uncovered and placed into fluid communication with the inlet and exhaust ports, respectively. The disc seals against the housing without the use of rubberized seals. The valve is only operable to maintain a vehicle at a single ride height.
Another type of height control valve is operable to maintain a vehicle at one of two ride heights. This type of valve, however, includes rubberized seals that seal a moving piston with respect to a valve housing. The piston moves to selectively place various ports of the housing in fluid communication with each other. The rubberized seals of the valve are subject to wear as the piston reciprocates, leading to their eventual failure.